Processing and Analysis of Experimental Data for the Impact Toughness of the Steel Quality J55 API 5CT Using Design Expert Software

In this paper the plate from the steel of quality grade J55 API 5CT and the process of pipe forming Ø139.7x7.72 mm and Ø219.1x7.72 mm with rectilinear seam is analysed. The impact of deformation level in the cold and mechanical properties of the steel coils before and after the forming of the pipes are elaborated and processed through Design Expert Software. For analysis it was used the planning method of the experiment. It was built the mathematical model for the experiment with one index (impact toughness - Kv) and with one factor (level of deformation in the cold), and with few levels and two blocks (before and after the forming of the pipes). Statistical analysis of experimental data for models of plate and pipe were obtained through Design Expert Software. Based on such date graphic representation for the influence of deformation rate on Charpy-V notch energy was generated. Application of the Design Expert Software helps quick and correct combinations of three criteria (treatments) in order to estimate the level of deformation throughout the bending of sheet and calibration, influence of the decrease of impact toughness during the forming of pipes.